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On Ubuntu 12.04 - actually Kubuntu, but I am using NetworkManager, so the configuration should be the same - I have configured a few VPN connections.

Now, if I have a long-running up- or download, how can I ensure that all network traffic is stopped immediately and unconditionally if the VPN connection breaks off?

What I am looking for is some method of getting notified (I don't want to poll!) of the change. The rest (e.g. inserting netfilter rules) I can handle myself. I just need to find out how to get notified about a change to an established connection.

In case it matters, the configuration I am using is based on tun0. If other details are required, let me know in a comment and I'll add them to the question.

What I have tried so far:

  • configure the main LAN connection (this is inside a VM, so there is only a LAN connection) to be manual
  • configure the VPN to be automatic

then I figured that this isn't the route I want to take anyway, because I want to start my script/program to get notified only whenever I activate the VPN. I am not running on VPN all the time, but most of the time.

So basically I need to register for some notification as soon as a particular VPN connection is established and then get notified if something happens to it in order to tear down the main connection automatically in response.

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up vote 1 down vote accepted

NetworkManager should be able to do this for you. From the man page:

Information about networking is exported via a D-Bus interface to any interested application, providing a rich API with which to inspect and control network settings and operation.

NetworkManager will execute scripts in the /etc/NetworkManager/dispatcher.d directory in alphabetical order in response to network events.


Each script receives two arguments, the first being the interface name of the device just activated, and second an action.



vpn-up: A VPN connection has been activated. The environment contains the connection UUID in the variable CONNECTION_UUID.

vpn-down: A VPN connection has been deactivated.

So it looks like you have two routes: tie into D-Bus to listen for events and act upon them, or drop some scripts into /etc/NetworkManager/dispatcher.d/. The latter seems the path of least resistance.

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Excellent, looks like what I was looking for. Thanks. – 0xC0000022L Jun 23 '13 at 15:17

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